cargo clippy tests

[spl]

Okay, so now I've figured out how to cargo clippy the tests (and all other targets), and these are the results. The warning type fixes are broken down into separate commits. All changes are, I think, pretty innocent.

[spl]

One of the annoying things about clippy is that it does not visit files that it has already checked. So you can touch files to force it to see them. But I never did that with the xdv directory... until now. In the future, keep this command in mind:

$ find src tests xdv -type f -exec touch {} +; cargo clippy --all-targets --all-features

[spl]

There are perhaps a lot of changes here. Each commit is isolated and commutative with the other commits, so you can consider them separately. I'm not sure 12 separate PRs are better than this. If prefer a different form of submission, let me know.

[codecov]

Codecov Report

Merging #352 into master will decrease coverage by <.01%.
The diff coverage is 13.11%.

@@            Coverage Diff             @@
##           master     #352      +/-   ##
==========================================
- Coverage   39.61%   39.61%   -0.01%     
==========================================
  Files         135      135              
  Lines       59494    59496       +2     
==========================================
  Hits        23569    23569              
- Misses      35925    35927       +2

Impacted Files	Coverage Δ
xdv/src/lib.rs	0% <0%> (ø)	⬆️
tests/executable.rs	21.83% <0%> (+0.24%)	⬆️
tests/util/mod.rs	45.19% <33.33%> (-1.81%)	⬇️

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[codecov]

Codecov Report

Merging #352 into master will decrease coverage by <.01%.
The diff coverage is 13.11%.

@@            Coverage Diff             @@
##           master     #352      +/-   ##
==========================================
- Coverage   39.61%   39.61%   -0.01%     
==========================================
  Files         135      135              
  Lines       59494    59496       +2     
==========================================
  Hits        23569    23569              
- Misses      35925    35927       +2

Impacted Files	Coverage Δ
xdv/src/lib.rs	0% <0%> (ø)	⬆️
tests/executable.rs	21.83% <0%> (+0.24%)	⬆️
tests/util/mod.rs	45.19% <33.33%> (-1.81%)	⬇️

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d69f5ff...91e3706. Read the comment docs.

[pkgw]

Yeah, 12 separate PRs would probably have been a bit overkill. This was not hard to review as presented. Thanks for all your work on cleaning up the codebase!